I have a problem with the Contact header in a SIP SUBSCRIBE request.

The situation is the following: FS is setup as a presence client using TLS as the transport layer. The server is to send presence information about a large number of mobile telephones.

The FS sends a SUBSCRIBE to the server, on a newly setup SSL connection. The SUBSCRIBE has in its Contact address 5061 as the port to be used for NOTIFYs to be send by the server.

I would like to use another port, namely the port used by the server in the new setup connection. It that possible and how? This would allow the server to respond on an established TLS connection.

I know there is another solution the problem involving the setup of a new secure connection initiated by the server, but I would prefer to change the port in our SUBSCRIBE request.

I should mention that we do not use registration towards the server.

Thanks /Jon